Feasibility of partial remelting process in globular microstructure preparation for semi-solid processing of M2 high-speed steel

Abstract

Feasibility of partial remelting process in producing the feedstock for semi-solid processing of M2 high-speed steel (HSS) has been investigated. The effect of reheating parameters, that is, heating rate, holding temperature and holding time on final microstructure of M2 HSS, has been studied. For this purpose, a series of experiments based on Taguchi method was employed to determine the required reheating cycles. The experiments were carried out in a resistance furnace and in an argon-controlled atmosphere to avoid any oxidation and decarburization. During any reheating cycle, the temperature of surface and core of the samples were recorded and compared with the furnace temperature. Microstructural evolution of the samples was then studied and the formation of a globular microstructure in holding time has been evaluated. The particle shape factor and globule size in each stage of experiments have been derived and its relation to other parameters has been studied. Finally, appropriate reheating cycle and parameters has been determined and two-dimensional plots of parameters versus shape factor are introduced as a process window for reheating cycle derived.